9-Chloro-1-methyl-7-phenyl-5,6-dihydro-13H-indolo[3,2-c]acridine

The title compound, C26H19ClN2, is a 5,6-dihydro-13H-indolo[3,2-c]acridine prepared by condensation of a 2,3,4,9-tetrahydro-1H-carbazol-1-one with 2-aminobenzophenone. The crystals undergo a destructive phase change upon cooling at varying temperatures between 270 and 200 K, depending on cooling rate and disturbance by vibration, thus indicating supercooling of the metastable room-temperature structure at lower temperature. The overall planarity of the indolo[3,2-c]acridine part of the molecule is interrupted by the saturated ethylene group, and the planes of the two halves exhibit a dihedral angle of 22.05 (6)° with each other while themselves being essentially planar. Packing is dominated by C—H⋯π interactions. No classical hydrogen bonds or stacking interactions are observed.

The title compound, C 26 H 19 ClN 2 , is a 5,6-dihydro-13Hindolo[3,2-c]acridine prepared by condensation of a 2,3,4,9tetrahydro-1H-carbazol-1-one with 2-aminobenzophenone. The crystals undergo a destructive phase change upon cooling at varying temperatures between 270 and 200 K, depending on cooling rate and disturbance by vibration, thus indicating supercooling of the metastable room-temperature structure at lower temperature. The overall planarity of the indolo[3,2-c]acridine part of the molecule is interrupted by the saturated ethylene group, and the planes of the two halves exhibit a dihedral angle of 22.05 (6) with each other while themselves being essentially planar. Packing is dominated by C-HÁ Á Á interactions. No classical hydrogen bonds or stacking interactions are observed.
Cg1 is the centroid of the ring C1-C6 and Cg2 is the centroid of the indole ring. Data collection and cell refinement: APEX2 (Bruker, 2008); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and Mercury (Macrae et al., 2008 (Iyer & Devi, 2008). A number of carbazole alkaloids with intriguing novel structures and useful biological activities were isolated from natural sources over the past decades which had attracted chemists to frame novel synthetic strategies towards the synthesis of carbazole and its derivatives. The continuous increase of isolable natural products as well as pharmacological action of these carbazole derivatives has generated synthetic interest; consequently the syntheses of carbazoles have been a vigorously active area of study (Knölker & Reddy, 2002, and references therein;Choi et al. 2008).
Based on the structural, biological and pharmacological importance of the carbazole derivatives, the present investigation was aimed to devise a viable synthetic route to prepare these classes of compound using different synthetic methodologies.
For our synthetic strategy 2,3,4,9-tetra-hydro-1H-carbazol-1-ones, prepared in our laboratory as potential precursors, have opened new avenues for the synthesis of highly functionalized carbazole derivatives. Based on these facts we have developed and reported an efficient syntheses of novel indoloacridines and have reported the crystallographic behavior of some of these compounds (Sridharan et al., 2009a,b). The current contribution presents the synthesis ( The phenyl ring is at an angle to the first plane of 77.81 (6)°.
The N-H group does not form a classical hydrogen bond in the solid state and no strong π-π stacking interactions are observed. Other than van der Waals dispersive forces the packing of the compound in the solid state is dominated by C-H···π interactions (Fig. 3). The two most prominent such interactions are between C10-H10B and the centroid Cg1 of the ring built by atoms C1 to C6 (the chlorine-substituted phenyl ring), and between C26-H26 and the centroid Cg2 of the indole ring with H···Cg distances of 2.96 and 2.51 Å (Table 1). Additional very weak C-H···C and N-H···C interactions are indicated in Fig. 3.
In a recent publication (Sridharan et al., 2009b) we reported the structure of the dehydrogenated derivative of the title compound. It crystallizes in a primitive inversion symmetric setting with a similar volume as for the structure of the title sup-2 compound. There are however no further reaching similarities between the structures of the two compounds. The hydrogenated molecule is essentially planar and packing, shape of the unit cell and location of the inversion centers are different for the two related compounds (Fig. 4).
After the completion of the reaction, the mixture was poured into crushed ice, extracted with chloroform, and the organic layer dried (Na 2 SO 4 ). The crude product obtained on removal of the solvent was purified by column chromatography over silica gel using petroleum ether:ethyl acetate (98:5) to yield the title compound. 1.26 g, 64%, m.p. 527-529 K. Single crystals suitable for data collection were grown by slow evaporation from a solution in ethanol.

Refinement
All H atoms were added in calculated positions with C-H bond distances of 0.97 (methylene), 0.93 (aromatic) and 0.96 Å (methyl) and an N-H distance of 0.86 Å. They were refined with isotropic displacement parameters U iso of 1.5 (methyl) or 1.2 times U eq (all others) of the adjacent C or N atom. Fig. 1. Synthesis of the title compound    (Sridharan et al., 2009b). The chlorobenzene part of the top molecule was used to define the overlay of the two compounds. The other molecules are created by the symmetry operations of their respective structures.